Chapter 14-Sample Size Determination

Question 1

Budget (most common)

Answer 1

after deduction of other project costs (e.g. research design, questionnaire development, data processing, analysis and reporting) the remaining budget determines the sample size

Question 2

Rule of Thumb

Answer 2

Potential clients may specify in their RFP (request for proposal) that they want a sample of 200, 400, 500, or some other size. Sometimes, this number is based on desired sampling error. In other cases, it is based on nothing more than past experience. e justification for the specified sample size may boil down to a “gut feeling” that a particular sample size is necessary or appropriate.

Question 3

number of subgroups to be analyzed

Answer 3

for example 400 is a large enough sample size, but then you have men vs. women so its down to 200, then you take into consideration age and it cuts the sample size down even more. is it enough?

Question 4

judgment

Answer 4

If all else fails, an estimate of the population standard deviation can be de- veloped based solely on judgment. Judgments might be sought from a variety of manag- ers in a position to make educated guesses about the required population parameters.

Question 5

statistical methods (best in theory, but hard to do)

Answer 5

1. estimate of the population standard deviation
2. the acceptable level of sampling error
3. the desired level of confidence that the sample result will fall within a certain range of true population values